The present invention relates to an improved hydrotrope for liquid detergent compositions. In particular, the invention relates to a novel and synergistic hydrotrope that is a combination of a polyethylene glycol ether of glycerin and an alcohol ethoxylate and is useful for surfactant based detergent compositions.
Liquid detergent compositions are used in a variety of cleaning activities. For example, they are used to machine wash and hand wash clothes, dishes, hard surfaces such as walls and glass, and automotive surfaces. Generally, each use dictates different desired performance characteristics for each type of detergent composition. For example, it is desired that liquid detergents used to machine wash clothes or dishes do not generate a high volume of foam because excessive foam can inhibit cleaning efficacy and be difficult to remove from the washing machine. On the other hand, it is desired that a detergent composition used to hand wash clothes, dishes, or automobiles (and similar vehicles) generate foam because the perception of cleaning quality is directly related to foam volume in these applications.
At the same time, the detergent composition should be easily dispersed, particularly when incorporated in an aqueous carrier, and have an appropriate viscosity, i.e., be free from gelling. To accomplish these and other objectives, it is known to add hydrotropes; for example an alcohol such as ethanol. Unfortunately, the use of ethanol raises flammability concerns and also tends to produce compositions that develop a skin on standing because of evaporation of the hydrotrope. Moreover, if more than a minimal amount of ethanol is required to prevent gelling, the compositions may impart the typical odor of ethanol that is difficult to cover with fragrances.
Thus, there is always a need for a detergent composition that satisfies a variety of performance characteristics such as foam generation, dispersability and viscosity control, compatibility with other formulation components, environmental safety and cost effectiveness.
The present invention provides such a composition by providing a novel hydrotrope that results in liquid detergents that have excellent dispersability, gelling/viscosity, odor and foaming characteristics. The novel hydrotrope is a combination of a polyethylene glycol ether of glycerin and an alcohol ethoxylate that synergistically provides improved performance characteristics beyond that which would be expected from their additive effects.
According to the present invention, a liquid detergent composition is provided that comprises from about 1% to about 90% of a main detergent surfactant and from about 1% to about 40% of a hydrotrope that is a combination of a polyethylene glycol ether of glycerin and a short-chain alcohol ethoxylate. The liquid detergent preferably is an aqueous detergent and thus can contain from about 1% to about 90% water. Nevertheless, it is desirable to provide a concentrated composition and, thus, the detergent preferably contains from about 1% to about 40% water.
The main detergent surfactant includes at least one surfactant selected from the group consisting of anionic, nonionic, amphoteric surfactants and mixtures thereof. The anionic surfactant includes but is not limited to the sulfated anionic surfactants, sulfonated anionic surfactants, sulfosuccinates, sulfosuccinamates, taurates, isethionates, salts of fatty acids, carboxylated alcohol ethoxylates, ether sulfates and combinations thereof. The nonionic surfactant includes but is not limited to the alkanolamides, amine oxides, alkoxylated alcohols, alkoxylated phenols, block polymers and co-polymers, alkoxylated amines, alkyl polysaccharides, glucosamides, sugar esters and combinations thereof. The amphoteric surfactant includes but is not limited to the monoacetates, diacetates, betaines, glycinates, imidazolines, imidazoline derivatives, monopropionates, dipropionates, hydroxy sultaines and combinations thereof.
Foam-enhancing agents may be added to the composition and, if added, are present in an amount from about 1% to about 40%. Although the foam-enhancing agent may be the same as one or more of the surfactants included as part of the main surfactant, typically the foam-enhancing agent will be different. The foam-enhancing agent is typically selected from the group consisting of amine oxides, amides, alkyl glucosides, and mixtures thereof.
The hydrotrope of the present invention can be used in conjunction with or to replace in whole or in part these foam-enhancing surfactants. Preferably, the hydrotrope of the present invention is used in conjunction with these foam-enhancing surfactants. In this instance, the presence of the hydrotrope of the present invention provides foam generation greater than without the presence of the novel hydrotrope.
In addition, the hydrotrope of the present invention can be used to replace in whole or in part the known hydrotropes such as the alcohols, diols, and triols. Generally, the ratio of the polyethylene glycol ether of glycerin to the short-chain alcohol ethoxylate ranges from about 1:20 to about 20:1, preferably from about 1:10 to about 10:1, and more preferably from about 1:3 to about 3:1.
In one embodiment, the hydrotrope consists essentially of a mixture of a polyethylene glycol ether of glycerin and a short-chain alcohol ethoxylate where they are the only added hydrotrope constituents present in the composition. In this regard, it is known that some surfactants such as ether sulfates, when commercially supplied, contain low molecular weight alcohols, such as ethanol, which if added to a detergent composition may be considered a hydrotrope. These low molecular weight alcohols are incorporated in the commercial products so that they are free-flowing liquids. Thus, in this embodiment, when it is stated in the specification and claims that the hydrotrope consists essentially of a mixture of a polyethylene glycol ether of glycerin and a short-chain alcohol ethoxylate where they are the only added hydrotrope constituents present it is meant to exclude any added alcohol, diol, or polyol as a hydrotrope but is not meant to exclude low molecular weight alcohol (e.g., ethanol) that may be present as part of the surfactant constituent. Thus, it is not meant to exclude any ethanol that is present in a commercially available surfactant such as an ether sulfate.
In one preferred embodiment of the present invention, a liquid detergent is provided that consists essentially of from about 1% to about 90% of one or more anionic surfactants, from about 1% to about 40% of one or more foam-enhancing agents, and from about 1% to about 40% of a hydrotrope. The hydrotrope in this embodiment is a mixture of an alcohol ethoxylate and an ethoxylated glycerin such that the hydrotrope comprises from about 90% to about 100% of a mixture of an alcohol ethoxylate and an ethoxylated glycerin, preferably such that the hydrotrope comprises 100% of a mixture of an alcohol ethoxylate and an ethoxylated glycerin. In other words, the resulting composition is substantially free or completely free from other added hydrotropes (excluding those present as a result of surfactant manufacturing such as ethanol present in commercially available ether sulfates).
In another embodiment of the present invention, a liquid detergent is provided that comprises from about 1% to about 90% of a main detergent surfactant selected from the group consisting of anionic, nonionic, amphoteric surfactants, and mixtures thereof and from about 1% to about 40% of a hydrotrope wherein the hydrotrope comprises at least about 50% of a mixture of a polyethylene glycol ether of glycerin and a short-chain alcohol ethoxylate. In this embodiment, the main detergent surfactant is preferably selected from the group consisting of anionic and nonionic surfactants and mixtures thereof. More preferably, the main detergent surfactant comprises predominantly one or more nonionic surfactants with the balance being one or more anionic surfactants. For example, the main detergent surfactant comprises from about 50% to about 90% of one or more nonionic surfactants and from about 10% to about 50% of one or more anionic surfactants.
The present invention is also directed to an improved liquid detergent composition containing one or more surfactants selected from the group consisting of anionic, nonionic, amphoteric surfactants and mixtures thereof, wherein the improvement comprises an effective amount of a hydrotrope to provide increased foam generation ability to the composition and wherein the hydrotrope comprises a mixture of an alcohol ethoxylate and an ethoxylated glycerin.
The present invention also includes a method of increasing the foam generation ability of a liquid detergent composition that comprises the step of adding an effective amount of a hydrotrope to the liquid detergent wherein the liquid detergent includes one or more surfactants selected from the group consisting of anionic, nonionic, amphoteric surfactants and mixtures thereof and wherein the hydrotrope is a mixture of an alcohol ethoxylate and an ethoxylated glycerin.
It is noted that, unless otherwise stated, all percentages given in this specification and the appended claims refer to percentages by weight.